ui: 模型选择栏布局重设计

- 新增渐变图标指示器
- select 更大圆角 + 更粗边框 + hover/focus 渐变高亮
- 能力标签改为独立彩色 pill（Think 紫色、Vision 青色）
- 箭头图标改为青色
- model-bar.js 适配新 badge 元素

index.html

@@ -47,6 +47,12 @@
 
     <!-- ═══════════════ 模型选择栏 ═══════════════ -->
     <div class="model-bar">
+        <div class="model-bar-icon">
+            <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
+                <path d="M12 2a7 7 0 0 1 7 7c0 2.38-1.19 4.47-3 5.74V17a1 1 0 0 1-1 1H9a1 1 0 0 1-1-1v-2.26C6.19 13.47 5 11.38 5 9a7 7 0 0 1 7-7z"/>
+                <line x1="9" y1="21" x2="15" y2="21"/>
+            </svg>
+        </div>
         <div class="model-select-wrap">
             <select class="model-select" id="modelSelect">
                 <option value="">正在加载模型...</option>
@@ -55,7 +61,10 @@
                 <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><polyline points="6 9 12 15 18 9"/></svg>
             </span>
         </div>
-        <span class="model-info-badge" id="modelInfoBadge" title="模型信息"></span>
+        <div class="model-badges" id="modelBadges">
+            <span class="model-badge think-badge" id="badgeThink" style="display:none;">🧠 Think</span>
+            <span class="model-badge vision-badge" id="badgeVision" style="display:none;">👁️ Vision</span>
+        </div>
     </div>
 
     <!-- ═══════════════ 聊天区域 ═══════════════ -->